1. Field of the Invention
The present invention is related to the control of image quality by image displays. More particularly, the present invention relates to a system for circuitry that provides control of image displays.
2. Description of the Related Art
Most image displays, being analog by design, employ color saturation, brightness, contrast and hue control circuitry, which works along with analog video signals. Similar circuits working with digitized video signals are used in post-processing film and video industry and are based on software driven microprocessor systems.
A new generation of digital image displays (for example, based on Liquid Crystal on Silicon (LCoS) technology, TFT-LCD, DLP and PDP), takes further advantage of its higher resolution by performing all video signal processing starting from the source in digital domain, thus eliminating the need for analog-to-digital (A/D) and digital-to-analog (D/A) converters in the signal path and avoiding digitizing artifacts in the displayed images.
There are several ways in which color projection can be performed using LCoS displays. One such example is referred to as “3-Chip Color” in which a series of prisms are arranged to form a color cube. Light, which typically originates from a lamp and then passes through a condenser lens to increase its uniformity (i.e. focus), subsequently passes through a dichroic filter to remove light outside the visible spectrum before striking a mirror, which directs the path of the light to the color cube.
After entering the cube, the light is subsequently split into three beams that project off three separate LCoS displays. Each of the respective LCoS displays has one of a red, green, or blue filter located in front. Each of the displays receives a different video signal with the correct image for its corresponding color. The cube then combines the reflected images that result in a final color image that is projected.
Another way that LCoS displays provide color is by a color wheel optical system, whereby light, which first passes through a condenser lens and a dichroic filter, subsequently passes through a color wheel that includes red, green and blue (and sometimes yellow and white) transmissive portions. The colored light may then pass through a quarter wave plate and subsequently reflect off the LCoS display and through a projector lens. The LCoS display changes color according to the particular color being projected (i.e. red, green, blue, and possibly even yellow) at multiples of the normal projection rate, so as to “fool” the eye into perceiving the projected images as an image in full color.
Yet another way that the color can be provided in, for example, TFT-LCD display is by the use of color dots, also fooling the perception of the eye to see the images in full color. By this method, a series of pixels have different color dots that are activated according to the color signal. The arrangement of the pixels and the particular ones turned on provides a perceived full color image to the human eye.
A single panel scrolling color method is yet another way that a full color image is perceived by the human eye. According to the scrolling method, the screen may, for example, be subdivided into different color images (such as red, green, blue, yellow, etc.). In the case of three color images, the sub-division can be into thirds that are vertically stacked, so that a vertical scroll of the different color images at speeds too fast to be detected by the human eye occurs, allowing for the perception of a full color image.
In all of the above methods (as well as others), the LCoS display devices require that the luminance/chrominance (Y/C) signals be converted to the red-green-blue (RGB) domain, as any display technology requires RGB signals. Most of the methods also require that the projected image be spatially rearranged (i.e. for a single panel scrolling color method the R, G and B components of the image must be presented to the display device according to the current position of the illumination color stripes). This kind of signal processing is preferably done in the digital domain due to higher accuracy and simplicity.
Accordingly, there is a need in the art to provide the consumer picture controls, such as brightness, contrast, color saturation and color hue, to be implemented digitally with minimal resources required to take further advantage of all-digital processing.